David Grinspoon

The reason you see so many volcanoes on Venus is partly due to the fact that there's virtually no erosion there. So on Venus, you're seeing features, some of which are hundreds of millions of years old on the surface. On Earth, we do not see any surface features nearly that old - you only see much more recent features.

Earth's biosphere gave birth to humans and our thoughts, which are now reshaping its planetary cycles. A planet with brains? Fancy that.

Part of the point of SETI has always been a search for answers about our own cosmic potential and destiny. If 'they' are out there, it means that there may be hope for us.

Earth is a stunningly lovely planet for so many reasons. Among these is the wondrous presence of curious, artful, inventive humanity.

Whenever I see a nighttime picture of Earth from space, with its glowing lights, I am stirred by its beauty.

Mars does not belong to 'America,' nor to Earth, nor to human beings.

Even as our unwitting alterations to Earth's carbon and hydrological cycles slowly make storms more damaging, our ability to monitor our planet from space and make reliable short-term forecasts have equipped us enormously to withstand them.

Literally, my earliest memory, my earliest vivid memory, is the Apollo 11 landing on the Moon. Yeah, I was in fourth grade, and I was just so captivated. And I think you'll find a lot of space scientists of my generation will say the same thing. Apollo was a big event for them.

NASA, and all the other spacefaring nations of the world, have agreed to a set of 'planetary-protection' principles, aimed at preventing the accidental contamination of another habitable world with organisms from Earth.

I will defend the NASA Earth Science Division with everything I've got.

If we gutted NASA Earth Science, it wouldn't be NOAA or some other agency that would take the lead. It would be the Chinese and the Europeans and the Japanese.

We're going to stop looking at Earth from orbit because we don't like what we are seeing and the conclusions that leads us to? That's nonsense.